I think for the main living areas, you should think about hanging family photos. You can supplement with mirrors, pottery, framed prints. Do a family excursion to one of your favorite museum and buys some prints for matting or framing.
In terms of accent pieces, I don't like furniture that doesn't have a purpose.
Given your tastes, I would check out furniture places in Adams Morgan:
http://washington.org/DC-focus-on/adams-morgan-shopping